Methylprednisolone sodium succinate has been recommended by some as beneficial in the treatment of low cardiac output and ischemic states. Many investigators have documented certain beneficial inotropic and chronotropic effects of this drug on the heart, including direct coronary artery vasodilation. In the renal circulation, various shock states and various drugs redistribute blood flow from the outer cortex to the inner cortex where juxtamedullary glomeruli have a greater capacity of retaining Na+. The technique of radioactive microspheres is used to determine if methyl-prednisolone is beneficial to normal dog hearts and kidney, and in addition to a region of the heart made "vulnerable" by reducing the mean distal left circumflex artery pressure to a level of around 20 mm. Hg.